Solar Walls Save Money

Canadian producer Daniel Messier describes the better air quality and lower heating costs as impressive. Using a solar wall to capture the sun's energy

Suzanne Deutsch | Nov 15, 2007

Canadian producer Daniel Messier describes the better air quality and lower heating costs as impressive.

Using a solar wall to capture the sun's energy for supplemental heat in nursery barns is saving Acton Vale, Quebec pork producer Daniel Messier $4,000 a year on his propane heating bill.

Six years ago, Messier installed SolAgra solar walls, hoping to slash his heating bills on two, 60 x 100-ft. nursery barns by at least 25%. The solar wall system works so well that his barns use about 30% less propane than similar barns in his region, he says.

“My yearly propane bill is around $10,000. My neighbor's bill tops $14,000,” says Messier. Their barns are similar in size, house approximately the same number of pigs and were built within a few years of each other.

“Since the integrator that supplies my piglets also owns the company that supplies my propane, my lower heating bill raised a big, red flag,” explains Messier. “They accused me of lowering the thermostat as soon as their technician left the farm. They wouldn't believe a word I said — as if I could lower the temperature by 8°F in a nursery that just received 1,200 piglets and still have great performance and a 3% mortality rate! They actually hid a black box in a stall, which recorded daily temperatures.”

How the Walls Work

Quebec winters get cold. When it's -22°F outside, keeping nurseries at 84°F can produce spectacular heating bills, he assures. In an effort to control expenses, Messier installed the system even though his integrator didn't recommend it.

“They were dead set against it,” Messier grins. “They said it would be a waste of money and likely would bring in too much heat in the summer. Were they ever wrong!”

Anyone who has spent a lazy day sunning themselves by a window on a cold winter day intuitively understands how solar heating works. Solar energy strikes an object and is converted to heat.

SolAgra solar walls are made of hollow, perforated sheet metal. The metal absorbs up to 95% of the sun's energy on cold, but sunny winter days. The Quebec Swine Improvement Centre (Centre de développement du porc du Québec, or CDPQ) found that readings peak above 100%. This high level of absorption is a combination of the sunlight striking the wall directly and the nearby snow acting as a giant reflector, bouncing additional light onto the wall. Since the wall doubles as the building's primary air intake during the winter, the sun warms the air as it passes through the perforations before entering the building.

Perforations are custom-made to allow between 1 and 20 cu. ft./minute (cfm)/sq. ft. of fresh air to enter the building. Perforations are calibrated to meet 100% of the building's ventilation needs from late fall to early spring.

The holes are very small in order to let only the first 0.04 in. of warm air on the metal's surface into the building. The bigger the solar wall, the smaller the holes. The smaller the holes, the greater the temperature gain, Messier explains.

The warmed air is pulled through the building by fans located on the north walls. A supplemental heating system is still needed on some cold days and often kicks on at night. Messier says that even with outdoor daytime lows of 14°F, indoor temperature readings held at 59°F. “That's 45 degrees I didn't have to heat with propane,” he exclaims.

Bypass Inlets Prevent Overheating

“Southerly facing walls, especially those at a southeast angle, receive much less energy in the summer because of the sun's high angle in the northern hemisphere, compared to its lower angle during the winter,” says Réal Savaria, owner of the Sherbrooke, Quebec firm, Solag.

“Nonetheless, the system has alternate air intakes with greater flows, which can bypass the solar collector,” he explains.

The system is great for getting rid of humidity and for drying nursery rooms after a thorough cleaning. In addition, the steady supply of dry air, year-round, means producers can increase ventilation without having to incur extra heating costs.

As a footnote, he adds that the system is oblivious to strong prevailing winds. Not only will the holes in the solar wall let a certain amount of air in, the air intake remains the same, whether it is windy or not. No more high or negative air pressure problems and the variations in temperature that go along with it.

Colors Absorb Differently

“Most people prefer black because it has a 94% efficiency, but all dark colors work well and blend in with the look of most buildings designed for industrial and agricultural uses,” says Savaria. “I tend to discourage clients from choosing bright red, for instance, because the efficiency drops to 59-60%.”

Payback Potential

Messier figured he would recoup his 2001 investment of $23,000 in less than five years. But any hesitation vanished when he heard that the Canadian government offered a 25% grant incentive for new “green energy” alternatives.

“Each square foot of wall, depending on where you are located and your (sun) exposure, is the equivalent of between $2 and $4/sq. ft. in propane savings, annually,” he says. “After 10 years, you're looking at savings of at least $20/sq. ft. The good thing is, once that initial investment is done, that's it for at least 25-30 years. It just keeps on giving and there's no maintenance to speak of.”

Dirt buildup is not an issue. The static pressure is spread over a very large surface area, so there is 80-100% less air per square foot entering the building through the wall, compared with normal air intakes. Messier has not cleaned the nursery wall since installing it six years ago. The little build-up that could occur is generally rinsed away whenever it rains, he says.

For optimal results, a solar wall should be installed on a southerly facing wall, whether it's retrofitted to an existing building or a new construction. Savaria says he'd rather tell clients outright if solar walls won't provide good results for their operation. As part of his services, he also helps producers navigate through the paperwork required to obtain the U.S. government's 30% tax credits. Further information can be obtained on Solag's website: www.solag.net[3].